1. Field of the Invention
The present invention relates to an imaging apparatus that obtains an image with a wide dynamic range on the basis of an image that has been imaged with standard exposure time and an image that has been imaged with short exposure time and an imaging device suitable for the imaging apparatus.
2. Description of the Related Art
As an imaging apparatus using an imaging device of this type, there is an imaging apparatus that generates an image with a wide dynamic range by imaging images with two kinds of exposure time (standard exposure time and short exposure time) in one frame period and replacing pixels with a maximum luminance value in the image that has been imaged with the standard exposure time with pixels in the image that has been imaged with the short exposure time (see, for example, JP-A-2003-198948).
In the imaging device for the imaging apparatus in JP-A-2003-198948, first, respective lines (pixel arrays) are sequentially reset from an upper side to a lower side in a plan view and charges are read out from the reset pixel arrays sequentially from one for which the standard exposure time has elapsed. The pixel arrays, from which charges have been read out, are reset sequentially from one for which predetermined time has elapsed. Charges are read out from the reset pixel arrays sequentially from one for which the short exposure time has elapsed. The imaging device realizes a rolling shutter in which the pixel arrays, from which charges after the standard exposure time are read out, the pixel arrays, for which a reset operation after the predetermined time is executed, and the pixel arrays, from which charges after the short exposure time are read out, move sequentially.
However, in the imaging device in the past, since the respective pixel arrays are simply reset sequentially, only the same short exposure time can be set for all the pixel arrays. Therefore, for example, in imaging a subject with high contrast, when the short exposure time is set short such that charges accumulated in the imaging device do not saturate, it is likely that a S/N ratio of charges (image signals), which are read out from the imaging device in a dark part with a small amount of incident light, deteriorate more than necessary. When the short exposure time is set long, image signals outputted from the imaging device saturate even in a bright part with a large amount of incident light. Thus, it is likely that, even if the pixels are replaced, an image to be generated does not have a wide dynamic range.